The present invention relates to methods and systems for producing a consumable aqueous extract from a solid raw material. Specific embodiments of the invention involve methods for forming concentrated aqueous extracts of roasted coffee useful in food, fragrance, and beverage products.
A variety of solid raw materials are commonly extracted with aqueous solvents, such as hot water, to form consumable aqueous extracts for use in foods, fragrances, or beverages. Common materials include roasted ground coffee, tea, and cocoa just to name a few. Typical and representative of currently employed methods and systems for performing such extractions are those used for brewing and extracting roasted coffee. Generally the prior art systems fall into two broad categories: small-scale home or commercial brewing equipment for producing beverages; and large-scale industrial extractors for producing concentrated extracts for use as flavorings or as raw materials for the production of instant coffee products. When used for the production of instant coffee products, the aqueous solvent is typically removed from the dissolved coffee solids by processes such as freeze drying or spray drying.
Typical prior art large-scale coffee extractors and associated extraction methods, especially when used to produce coffee extracts for the subsequent production of instant coffee, are designed to maximize the yield of soluble coffee solids in the extract from a given quantity of ground roasted coffee. This is done for economic reasons: the more soluble coffee solids extracted from a given quantity of roasted coffee raw material, the greater the quantity of final instant coffee product derived upon removal of the water. To this end, typical prior art large-scale coffee extractors are designed for the exhaustive extraction of typically low-grade ground coffee and not for production of a high quality, flavorful, fragrant extract. Many typical prior art extractor systems of this type employ one or more columns having fixed beds of ground roasted coffee. Representative of such a system is the one described in U.S. Pat. No. 3,830,940 to Sivetz. Many prior art systems employ circulation of hot water through the columns where the water flows into the bottom of each column and exits from the top, thus tending to expand and agitate the bed. Very hot extraction water, often in excess of 160 degrees C., is often fed to the column containing the most spent coffee (the coffee that has had the most solids already extracted) in order to thermally hydrolyze the coffee to enable extraction of additional solids, which are essentially free of flavor and fragrance. Often, the extract may be recycled through the columns to further increase the extent of the extraction of the ground roasted coffee. While such systems and methods are useful for exhaustive extraction, they are not ideally suited for producing high quality coffee extracts with desirable sweetness and flavor characteristics. The relatively long extraction times (for example greater than 1 hour), high water temperatures, and levels of dilution used in certain prior art extraction processes can result in extracts having a relatively high concentration of components that are bitter or have poor flavor characteristics, which are often passed on to the dried instant coffee products produced from such extracts. Many of the concentrated coffee extracts commonly employed as flavor components in the food industry (e.g. as flavorings for coffee ice cream, iced coffee beverages, and coffee syrups) are produced by reconstituting such poor quality instant coffee products with water or other materials.
It is understood that sweeter and more flavorful coffee extract can be produced near the beginning of an extraction cycle, when the fresh ground coffee has been in contact for a relatively short period of time with only a relatively small quantity of water, than can be produced later in the extraction process after the coffee has been exposed to additional quantities of water and more exhaustive extraction. Attempts have been made to improve upon the quality and flavor of coffee extracts and instant coffee products produced by large scale extraction processes. One such method described in U.S. Pat. No. 4,534,985 to Gasuu (""985) discloses an industrial scale continuous extraction process and apparatus for the extraction of coffee or tea. The apparatus involves a complex system using a number of extractant beds and extraction zones, where the beds are movable between zones by rotation of the apparatus. The process reduces the total time of the extraction process when compared to more conventional prior art extraction methods. The ""985 patent also discloses the use of compressed air or an inert gas in a xe2x80x9crecovery stationxe2x80x9d of the apparatus to maximize recovery of the residual liquid present in the spent grounds after extraction.
Various smaller scale brewing/extraction methods for home or commercial use are known in the prior art for producing beverages from solid raw materials such as coffee, tea and cocoa. Common methods include steeping or infusion in a static volume of hot water (i.e. steeping a tea bag in a cup of hot water), steam-driven percolation, and extraction via a continuous flow of hot water under the force of gravity through a bed of solid extractable material, typically coffee. The latter method described is the one typically employed in home xe2x80x9cdrip methodxe2x80x9d coffee makers. All of these methods typically produce a relatively dilute beverage-strength extract (typically, 1 lb of ground, roasted coffee will yield about 320 oz. of beverage-strength extract). In addition, because of the continuous addition of water used to drive the flow of extract through the bed, the beverages produced can contain undesirable quantities of bitter or off-flavor components.
An improvement to most of the above described methods for producing a sweeter, more flavorful, more fragrant, and more concentrated coffee beverage is the espresso method of coffee extraction. The espresso method of extraction typically employs a small-scale home or commercial brewing apparatus utilizing a less exhaustive extraction method to produce a relatively sweet, more concentrated beverage. Typically, a higher ratio of ground coffee to hot water is employed, for example about 1 lb. of ground roasted coffee may typically yield about 64-128 oz of coffee beverage. In order to allow sufficient contact time between water and the ground coffee, the method typically utilizes a finely ground coffee (e.g. 14 gram weight) with hot water being forced through the bed of grounds contained in the brew chamber by additional pressurized hot water. Most typical currently employed espresso type extraction devices are capable of producing only relatively small quantities of extract during each extraction cycle. In addition the quality of the beverage can be very dependant on the grind and packing of the coffee, which dictates the back pressure developed by the flowing water during the extraction, and the extraction time for a given total volume of beverage. A lack of control over these variables can lead to a poor or inconsistent quality of extract. Also, since hot water is typically used to force extract from the bed of ground coffee during the entire extraction process, an undesirable level of extraction may still occur, yielding an extract which is too dilute, and not ideally suited for use as a food or flavor additive without a subsequent, undesirable removal of excess aqueous solvent from the extract.
A variety of small-scale espresso style coffee brewers have been described which attempt to improve upon the performance of conventional espresso brewers. U.S. Pat. No. 5,127,318 to Selby (""318) and U.S. Pat. No. 5,473,973 to Cortese (""973) both disclose an apparatus and process for extracting espresso type coffee in which the pressure within the extraction region is regulated by a biased valving arrangement on the outlet line downstream of the coffee bed. The valves are designed to remain closed during the initial pressurization of the extraction chamber by hot water until a preset pressure is reached that can overcome the bias of the regulating valve. When such pressure is reached, the valve opens for flow and maintains a relatively constant pressure in the extraction chamber during the remainder of the extraction process relatively independent of the grind or packing of the coffee. In the disclosed systems, the pressure constantly rises until a predetermined pressure is reached, at which point, flow immediately commences.
U.S. Pat. No. 5,267,506 to Cai (""506) discloses an apparatus for automatically brewing espresso coffee and includes one embodiment where pressurized steam generated by a heating unit is passed through the coffee grounds to purge liquid so that the grounds will not drip when the brew chamber is removed.
U.S. Pat. No. 5,337,652 to Fischer et al. (""652) discloses an espresso machine and method utilizing a biased pressure relief valve down stream of the brewing chamber similar to U.S. Pat. No. 5,127,318 (""318) and U.S. Pat. No. 5,473,973 (""973) described above. The biased valve prevents flow from leaving the discharge line until the pressure within the chamber rises to a fixed predetermined level; immediately thereafter, the valve opens and maintains a relatively constant pressure within the brew chamber during the remainder of the extraction. The ""652 system also includes an air pump with an outlet line in fluid communication with the water heating chamber. The air pump is used at the end of the brewing cycle to pump air through the coffee grounds in order to dry the coffee and produce a foamy head. The air from the pump is directed to the brewing chamber from the hot water compartment via a relatively complex automated valving/switching mechanism on a flow control manifold located within the water heating chamber. The air supplied to the brewing chamber in the ""652 system passes through the water heating chamber before entering the brewing chamber thus adding heat and moisture to the gas. The ""652 system is a relatively low pressure system with a maximum operating pressure disclosed of about 3.5 bar (about 50 psi).
While some of the above cited systems and methods for producing consumable extracts from solid raw materials represent, in some cases, useful contributions to the art of producing consumable extracts, there exists a need for improved methods and systems for producing variable quantities, including large volumes, of consumable extracts, including highly concentrated extracts, from solid raw materials, the extracts having desirable sweetness, flavor, and fragrance characteristics.
Accordingly, it is an object of the present invention to provide improved methods and apparatus able to controllably produce highly concentrated or less highly concentrated consumable extracts having excellent and desirable sweetness, flavor, and fragrance qualities from solid raw materials.
One aspect of the invention involves a method of extracting a consumable material from a solid raw material. The method involves first forming a quantity of solid raw material in an enclosed volume that is greater than the volume of the solid raw material. An aqueous solvent is then introduced into the enclosed volume. The aqueous solvent is made to flow through the quantity of material to form an aqueous extract from the solid raw material. The flow of aqueous solvent through the quantity of material is discontinued after a predetermined total volume of the aqueous solvent has passed through the material. A flow of a gas is then established through the quantity of material to remove any remaining aqueous extract from the material. The gas is supplied to the enclosed volume through an inlet line that is in fluid communication with the enclosed volume. The gas is supplied from a source of compressed gas external to the enclosed volume.
In another aspect, the invention involves a method for forming an extract containing a consumable material from a solid raw material. The method involves forming a quantity of solid raw material in an enclosed volume that is greater than the volume of the solid raw material. The enclosed volume includes at least one inlet line and one outlet line. With the outlet line closed, the enclosed volume is filled with a predetermined volume of an aqueous solvent. The enclosed volume is then pressurized to a predetermined and controllable pressure by supplying a fluid under pressure from a source of pressurized fluid external to the enclosed volume through an inlet line to the enclosed volume. The pressure is maintained in the enclosed volume under non-flow conditions for a predetermined and controllable period of time. The outlet line is then opened to collect an aqueous extract from the enclosed volume.
In another aspect, the invention provides a method of extracting a solid raw material to form an extract containing a consumable material. The method involves establishing a bed of solid raw material, supplying a volume of aqueous solvent to the bed, pressurizing the solvent and bed to a predetermined and controllable pressured level, maintaining the resulting pressure for a desired period of time under non-flow conditions, and establishing a flow of aqueous extract from the bed. Aqueous extract is then removed from the bed with a gas.
In yet another aspect, the invention provides a method for removing spent extractable solid material from an extraction vessel without the need for disassembly of the vessel. The vessel, according to the invention, encloses an internal volume and has at least one filter element. The vessel is constructed and arranged to contain a desired quantity of solid raw material. The vessel also has at least one inlet flush line and at least one outlet waste line. Prior to performing the method, the vessel contains a quantity of spent solid raw material. The method comprises first flowing a pressurized fluid through at least one inlet flush line. thus entraining and removing, with the flow of pressurized liquid, the spent material through the outlet waste line while essentially simultaneously back flushing the filter element.
In yet another aspect, the invention involves a method for forming a consumable extract from a solid raw material. The method includes at least partially filling an extraction vessel, which encloses an internal volume and has at least one inlet line and at least one outlet line, with a quantity of solid raw material. A flow of liquid solvent is then established through the material to form an extract from the solid raw material. The flow of liquid solvent through the bed is discontinued after a predetermined volume of the liquid solvent has passed through the material. A flow of a gas is then established through the material to remove extract from the material for collection. The gas is supplied to the vessel through an inlet line from a source of compressed gas external to the vessel.
In yet another aspect, the invention provides a method for extracting a solid raw material to form a consumable extract. The method includes at least partially filling an extraction vessel, which encloses an internal volume and has at least one inlet line and at least one outlet line, with a quantity of solid raw material to form a bed of the material. With the outlet line closed, the vessel is filled with a predetermined volume of liquid solvent. The predetermined volume is equal to or greater than the void volume present in the bed. The internal volume of the vessel is then pressurized to a predetermined and controllable pressure by supplying a fluid under pressure from a source of pressurized fluid external to the vessel through an inlet line to the vessel. The pressure in the vessel is maintained under non-flow conditions for a predetermined and controllable period of time before an outlet line is opened to collect the consumable extract from the vessel.
The invention also provides apparatus for forming a consumable extract from a solid raw material. In one embodiment, the apparatus comprises a sealable extraction vessel including an upper surface, a lower surface, and enclosing an internal volume. The upper surface provides fluid communication between an internal volume and one or more lines, which are constructed and arranged for fluid flow therethrough. Each of the lines includes at least one valve, with at least one of the lines being connected to an external source of heated, pressurized water, and at least one other line being connected to an external source of compressed gas when the apparatus is an operable configuration. The lower surface provides fluid communication between the internal volume and at least one line, which is constructed and arranged for fluid flow therethrough and includes at least one controllable valve. The internal volume of the vessel is constructed and arranged to contain a quantity of solid raw material and includes at least one filter element constructed and arranged to retain the material within the vessel during at least part of the extraction operation.
In another aspect, the invention provides an apparatus, which may by flushed-out without the need for disassembly, for forming a consumable extract from a solid raw material. The apparatus comprises a sealable extraction vessel enclosing an internal volume where the internal volume is constructed and arranged to contain a quantity of solid raw material. The internal volume further includes at least one filter element therein, which is constructed and arranged to retain the material within the internal volume during extraction. The internal volume of the vessel is in fluid communication with at least two lines, each constructed and arranged for fluid flow therethrough, with at least one of the lines being connected to an external source of pressurized liquid, and at least one other of the lines being in fluid communication with an outlet port on the vessel and connected to a waste disposal system when the apparatus is in an operable configuration. The lines are positioned in fluid communication with the internal volume of the vessel to enable spent solid raw material to be removed from the vessel through the outlet port, while simultaneously back flushing the filter element, without need for disassembly of the vessel.
The invention also provides an aqueous coffee extract obtained by extraction of a quantity of roasted coffee including at least one chosen variety of roasted coffee and having at least about 6% wt dissolved coffee solids. The extract retains an effective amount of the varietal flavor and fragrance components characterizing the particular variety, or mixture of varieties, of roasted coffee from other varieties.
Other advantages, novel features, and objects of the invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings, which are schematic and which are not intended to be drawn to scale. In the Figures, each identical or nearly identical component that is illustrated in various Figures is represented by a single numeral. For purposes of clarity, not every component is labeled in every Figure.